build: use golangci-lint (#20295)

* build: use golangci-lint

This changes build/ci.go to download and run golangci-lint instead
of gometalinter.

* core/state: fix unnecessary conversion

* p2p/simulations: fix lock copying (found by go vet)

* signer/core: fix unnecessary conversions

* crypto/ecies: remove unused function cmpPublic

* core/rawdb: remove unused function print

* core/state: remove unused function xTestFuzzCutter

* core/vm: disable TestWriteExpectedValues in a different way

* core/forkid: remove unused function checksum

* les: remove unused type proofsData

* cmd/utils: remove unused functions prefixedNames, prefixFor

* crypto/bn256: run goimports

* p2p/nat: fix goimports lint issue

* cmd/clef: avoid using unkeyed struct fields

* les: cancel context in testRequest

* rlp: delete unreachable code

* core: gofmt

* internal/build: simplify DownloadFile for Go 1.11 compatibility

* build: remove go test --short flag

* .travis.yml: disable build cache

* whisper/whisperv6: fix ineffectual assignment in TestWhisperIdentityManagement

* .golangci.yml: enable goconst and ineffassign linters

* build: print message when there are no lint issues

* internal/build: refactor download a bit

internal/build/download.go

@@ -0,0 +1,149 @@
+// Copyright 2019 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package build
+
+import (
+	"bufio"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// ChecksumDB keeps file checksums.
+type ChecksumDB struct {
+	allChecksums []string
+}
+
+// MustLoadChecksums loads a file containing checksums.
+func MustLoadChecksums(file string) *ChecksumDB {
+	content, err := ioutil.ReadFile(file)
+	if err != nil {
+		log.Fatal("can't load checksum file: " + err.Error())
+	}
+	return &ChecksumDB{strings.Split(string(content), "\n")}
+}
+
+// Verify checks whether the given file is valid according to the checksum database.
+func (db *ChecksumDB) Verify(path string) error {
+	fd, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer fd.Close()
+
+	h := sha256.New()
+	if _, err := io.Copy(h, bufio.NewReader(fd)); err != nil {
+		return err
+	}
+	fileHash := hex.EncodeToString(h.Sum(nil))
+	if !db.findHash(filepath.Base(path), fileHash) {
+		return fmt.Errorf("invalid file hash %s", fileHash)
+	}
+	return nil
+}
+
+func (db *ChecksumDB) findHash(basename, hash string) bool {
+	want := hash + "  " + basename
+	for _, line := range db.allChecksums {
+		if strings.TrimSpace(line) == want {
+			return true
+		}
+	}
+	return false
+}
+
+// DownloadFile downloads a file and verifies its checksum.
+func (db *ChecksumDB) DownloadFile(url, dstPath string) error {
+	if err := db.Verify(dstPath); err == nil {
+		fmt.Printf("%s is up-to-date\n", dstPath)
+		return nil
+	}
+	fmt.Printf("%s is stale\n", dstPath)
+	fmt.Printf("downloading from %s\n", url)
+
+	resp, err := http.Get(url)
+	if err != nil || resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("download error: code %d, err %v", resp.StatusCode, err)
+	}
+	defer resp.Body.Close()
+	if err := os.MkdirAll(filepath.Dir(dstPath), 0755); err != nil {
+		return err
+	}
+	fd, err := os.OpenFile(dstPath, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0644)
+	if err != nil {
+		return err
+	}
+	dst := newDownloadWriter(fd, resp.ContentLength)
+	_, err = io.Copy(dst, resp.Body)
+	dst.Close()
+	if err != nil {
+		return err
+	}
+
+	return db.Verify(dstPath)
+}
+
+type downloadWriter struct {
+	file    *os.File
+	dstBuf  *bufio.Writer
+	size    int64
+	written int64
+	lastpct int64
+}
+
+func newDownloadWriter(dst *os.File, size int64) *downloadWriter {
+	return &downloadWriter{
+		file:   dst,
+		dstBuf: bufio.NewWriter(dst),
+		size:   size,
+	}
+}
+
+func (w *downloadWriter) Write(buf []byte) (int, error) {
+	n, err := w.dstBuf.Write(buf)
+
+	// Report progress.
+	w.written += int64(n)
+	pct := w.written * 10 / w.size * 10
+	if pct != w.lastpct {
+		if w.lastpct != 0 {
+			fmt.Print("...")
+		}
+		fmt.Print(pct, "%")
+		w.lastpct = pct
+	}
+	return n, err
+}
+
+func (w *downloadWriter) Close() error {
+	if w.lastpct > 0 {
+		fmt.Println() // Finish the progress line.
+	}
+	flushErr := w.dstBuf.Flush()
+	closeErr := w.file.Close()
+	if flushErr != nil {
+		return flushErr
+	}
+	return closeErr
+}